Re: 20 ppm clock tolerance for WIS
Hi Gary,
At 4:33 PM -0400 00.5.31, Gary Nicholl wrote:
> Bottom line is that you bring up a good point to which I don't have a
> good answer. I guess I will just open it up to the rest of the group
> for discussion.
As a Carrier guy, I would like to put some comments on your Ottawa proposal;
http://grouper.ieee.org/groups/802/3/ae/public/may00/nicholl_1_0500.pdf
In summary,
(1) I agree that your SONET(-compliant) PHY will have market.
(2) I am not yet convinced why 802.3ae should define 'SONET-grade' OAM&P.
(3) We can use B1 (or B3) as performance monitor for the BER up to 10^-5.
(1) SONET(-compliant) PHY will have market
Assuming that adopting the SONET jitter spec for WIS, your proposal is
not only 'SONET-compatible' but also 'SONET-compliant'. It would work
well in our installed base SONET/WDM infrastructure as your POS
interfaces have done today. As for the SONET jitter spec, we will pay
some premium in 'SONET-grade' PMD when we need to connect it to the
installed base SONET equipment; this is quite similar what Bruce Tolley
has pointed out in the recent PMD discussions;
At 2:58 PM -0700 00.5.30, Bruce Tolley wrote:
> There is no threshold of pain in regard to cost, since if I cannot sell to
> my installed base THIS BUSINESS IS DEAD ON ARRIVAL.
(2) Do we need 'SONET-grade' OAM&P in 802.3ae?
In my sense, your proposal to add B2/K1/K2/M1 bytes is not the 'minimal
SUBSET of SONET functionality' but 'ordinary SET of SONET functionality'.
Your proposal has already satisfied the ITU-T Recommendation G707 that
has defined the reduced SOH functionalities interface (Table6/G707).
It sounds like 'SONET-grade' OAM&P to me.
As I understand, WAN-PHY proposal shown in the David Martin's presentation
at Albuquerque ('Why WAN-PHY?') can be now interpreted as follows;
http://grouper.ieee.org/groups/802/3/ae/public/mar00/bottorff_2_0300.pdf
(A) need mechanism that slowing the MAC rate to 9.29 Gb/s
(B) define WIS accommodating 64/66 PCS output into SONET payload
(C) avoid 'SONET compliant' management, jitter, and systems.
define minimal OAM&P functionality for WAN access/dark fiber.
With this minimal WAN-PHY definition alone, we can enjoy inexpensive jumper
access to SONET/WDM infrastructure via ELTE that would be tolerable to LAN
grade optics & jitter specifications. ELTE in SONET domain will provide
the SONET-grade OAM&P using B2 & K1/K2.
In this sense, I am not convinced yet why 802.3ae should define 'SONET-
compliant' PHY. Please be sure that I am not saying we won't buy the
'SONET-compliant' PHY; just wondering why minimal WAN-PHY would not be
enough for the 802.3ae standard. If you want, you can freely implement
any additional SONET(-compliant) function as you like. It had better be
vender specific. Basically SONET K1/K2 protection is very hard to
assure interoperability since it requires fast negotiation between the
link partners; we have to solve precise timing issues especially when we
run into the dual-fault conditions. This is why SONET is often referred
to be non-interoperable between the different vendors......
I think 802.3ae had better be stuck with minimal OAM&P functionality
that provides simple state-reporting mechanism such as J0, B1, and G1;
these are all free from destroying interoperability.
(3) Performance Monitoring by B1
In your presentation slides#8, you have said that B1 (Bit Interleaved
Parity 8) is not useful for performance monitoring. This is not true to
me; in OC192, B1 can be used to monitor the BER up to 10^-5 by using simple
compensation curve. Yes, we CAN distinguish between BERs higher than 10^-7.
In detail please refer to Figure 2 in
Y. Yamabayshi et al. 'High-speed regenerator section terminating LSIs'
Electronics Letters, 11th Nov. 1993 Vol.29, No.23. pp. 2057-2058
Also I would like to point out that ITU-T Recommendation G.783 has defined
the performance monitoring (Signal Degrade) threshold at 10^-5 to 10^-9.
Therefore I think we do not necessarily require B2 at least at 10Gb/s.
Best Regards,
Osamu
At 4:33 PM -0400 00.5.31, Gary Nicholl wrote:
> At 06:56 PM 5/30/00 , Praveen Kumar wrote:
>>You recommend using "LAN PHY jitter specs". This makes the WIS
>>incompatible with installed base SONET . This doesn't seem to meet your
>>goal of being compatible with installed OC-192 SONET
>>infrastructure. Please clarify.
>
> A good point. This probably does require some clarification. I guess
> using the word 'recommend' might have been too strong because this is
> an area which I believe still requires some further discussion.
> Personally I would agree with you in that the only way to ensure
> compatibility with the installed SONET based transport infrastructure
> would be to use SONET jitter specs. This is the same conclusion we
> came to about 12-18 months ago in the OIF when we went down a similar
> path of investigating relaxed jitter specs for Packet-Over-SONET
> (POS) interfaces in order to lower cost. At the time this was
> strongly opposed by both network operators and equipments suppliers.
> If I remember correctly companies like British Telecom, AT&T, Marconni,
> Lucent and Nortel were the most vocal in opposing any changes to the
> jitter specifications.
>
> However there are some other points we need to consider here. Unlike
> the issues of clock tolerance and overhead there probably is a
> significant cost associated with meeting SONET jitter specs (or so I
> have been told by a number of transceiver vendors). I also believe
> there is a strong desire within the group to use the same PMDs
> (optics) for both the LAN and WAN phys, so therefore burdening the PMD
> with meeting SONET jitter specs might add a lot of unnecessary cost and
> complexity to the LAN application.
>
> Bottom line is that you bring up a good point to which I don't have a
> good answer. I guess I will just open it up to the rest of the group
> for discussion.
-----------------------------------------
Osamu ISHIDA
NTT Network Innovation Laboratories
TEL +81-468-59-3263 FAX +81-468-55-1282